1. Field of the Invention
The present invention relates to a method of producing a lot of blanks usable for producing bearings in the form of a press worked bush. The present invention relates also to a method of producing a lot of bearings in the form of a press worked bush using thus produced blanks. Further, the present invention relates to a notch forming and cutting die for producing blanks as well as a die assembly including the aforesaid notch forming and cutting die.
More particularly, the present invention relates to a method of producing a lot of blanks usable for bearings in the form of a press worked bush (hereinafter referred to simply as bush) which has four corner edges chamfered so to assure that no chamfering operation is required after completion of production of bush bearings as well as a cutting die employable for producing blanks of the abovementioned type. Further, the present invention relates to a method of producing a lot of bush bearings of the type having four circular corner edges chamfered, the method including the steps of feeding a strip of metallic material having a predetermined width to a die assembly, forming a plurality of V-shaped notches on both the surfaces of material, the notches on the one surface of material being located in alignment with those on the other surface thereof, cutting off material at the joint area where the adjacent blanks are jointed to one another via the final V-shaped notch, bending thus obtained blank to the U-shaped configuration and then bending it to the circular configuration, wherein press working in each of the steps is achieved on a single straight line by simultaneous die closing and opening operation without any interruption. Moreover, the present invention relates also to a die assembly employable for carrying out the foregoing method of producing bush bearings.
2. Description of the Prior Art
Chamfered portion on the end face of a cylindrical bearing comprising bush press worked by press machine is generally prepared usually by machining operation for the following purposes.
1. to inhibit occurrence of local contact with the opponent shaft member, PA0 2. to assure that the bearing is brought in proper sliding contact with the opponent shaft member, PA0 3. to make it easy to fit the opponent shaft member to the bearing, PA0 4. to make it easy to press fit the bearing to a housing, PA0 5. to inhibit occurrence of malfunction relative to routine handling due to existence of shaft corner (edge portion) or the like.
Size and configuration of chamfered portion are specially determined in some case in dependence on its purpose but it is generally prepared in consideration of thickness and diameter of the bearing. Usually, larger and thicker bearing has wider chamfered portion and smaller and thinner bearing has narrower chamfered portion. As is widely known, chamfered portion is formed by cutting corner edge by an inclination angle of 45 degrees. When the chamfered portion has a length of 1 mm, it is represented by a symbol of 1C and when it has 2 mm, it is represented by a symbol of 2C. The end face of a chamfered bearing bush is constituted by two inclined faces at both the inner and outer circular corner edges and a flat end face extending at a right angle relative to the axis line of the bush.
Bearing bush made of metallic material such as cast copper alloy or the like is usually subjected to chamfering around both the inner and outer circular corner edges at the same time when finish machining is carried out by lathing or the like. On the other hand, in case of bush bearing made of metallic piece by press working particularly when it has a smaller diameter, thing is different because of the fact that machining is complicated and takes long time. Namely, chamfering is not effected after a product of bush is obtained but it is effected during production of blank. This type of method was already recognized as a very advantageous method and it was put in practical use.
In connection with this method the inventors invented blanks usable particularly for producing a lot of press worked bushes having a smaller diameter, each of the blanks being such that it had no flat end face but the end part was constituted by a combination of inclined faces, as well as a cutting die for producing these blanks. According to the prior invention it was found that particularly in case bearing bushes having a smaller diameter the object of chamfering was satisfactorily accomplished by inclined end faces and therefore no inconvenience was experienced when they were used practically. However, the conventional press worked bushes failed to meet requirement for flat end face mainly from the viewpoint of appearance particularly in case of a larger diameter.